Apparatus for spinning solutions of high polymers



March 18, 1952 P. SALE ETAL 2,589,870

APPARATUS FOR SPINNING SOLUTIONS OF HIGH POLYMERS Filed June 3, 1949 113.5 7: H. Tr i/Llai Patented Mar. 18, 1952 APPARATUS FOR, SPINNING SOLUTIONS OF HIGH POLYMERS Pierre Sal, A La Berni-Lune, and Joseph A.

Trillat, Lyon,

France, assignors to Societe' Rhodiaceta, Paris, France, a French company Application June 3, 1949, Serial N 0. 96,882 In France February 5, 1949 Claims.

It is customary in the spinning .of solutions of high polymers, such as for examplecellulose derivatives (cellulose xanthogenate and esters or ethers of cellulose), or synthetic polymers (polyvinyl derivatives, polyamidine derivatives, etc.)

to protect the apertures of spinnerets by means of a filter called garniture.

The present invention relates to a unit or device for spinning solutions of high polymers, which renders it possible to obtain surprisingly interesting results from a technical point of view in so far as it extends, in a manner unknown up to date, the period of technical use of a spinneret which can be used now for several months without alteration, even with interruptions of several days.

This remarkable result, which is of great economic and technical interest, has been attained by utilizing in the spinning of high-polymer solutions a unit comprising:

A spinneret plate which consists of rigid metal and is provided with extrusion orifices having a cross section at the inlet which is at least fifty times larger than the cross section at the outlet;

Arranged directly above said plate and in contact with it on a surface comprising all of the orifices and in such a manner that the spinning solution could not pass around without penetrating it is a special filter comprising at least one fabric formed of threads having a substantially cylindrical cross-section, in which the average width of the gaps left between the threads by their crossing is smaller than the cross-section of the extrusion apertures at their outlet;

A device for preliminary filtration which may contain at least one fabric similar to that mentioned above and which should be separated from the special filter by a space which allows the solution issued at all points of the preliminary filter to reach any of the extrusion orifices.

Numerous embodiments may be used in obtaining such units, with regard to the nature of the various elements or their assembling.

As to the nature of said elements, the spinneret plate may advantageously consist of unoxidizable steel, the thickness of which is determined by the bending stresses which it has to undergo as a function of its diameter, and the pressure of extrusion. It may be provided with holes of any desired shape. It has been found that in order to obtain a sufficient spinning time before clogging it is necessary that the cross section of the orifices at the inlet be equal to at least 50 times the cross section at the outlet. Moreover, this proportion may with advantage attain 2 -200 or even 10,000 to 80,000. The tissue forming the special filter may consist of substantially cylindrical threads of any kind: bronze, nickel, synthetic materials, particularly superpolyamides or vinyl polymers and analogous materials. Tightening of the threads, which is necessary to obtain very fine interstices, may be attained either directly or by means of an aftertreatment causing contraction. It has been found that in order to obtain an improvement of the spinning conditions, it is necessary to use at least one of these tissues, which may have for example a plain weave or satin weave. However, it is of advantage to use several layers which are eventually assembled by welding the edges, gluing or setting, the number of the layers being limited only by the resulting increase of pressure. In all cases in which several layers of fabric are present, they may comprise layers which are of different types with regard to fineness or with regard to weave. The device for preliminary filtration may also comprise one or more layers of analogous fabrics eventually assembled, welded or set together, or fabrics of different weave or tightness may be used. This device may also comprise grids for detaining coarse impurities, fabrics of the usual type, sheets of natural or artificial fibers which are carded or not, with separating spaces between the various materials or filter layers, etc.

As far as the assembling is concerned, there are three essential conditions to be met by the device used, i. e. the following: (1) The special filter should be in direct contact with the spinneret plate on a surface comprising all of the orifices; (2) the solution should not be able to avoid this filter and particularly it should not infiltrate through'the edges toward the holes or orifices of the spinneret; and finally, (3) it is necessary to provide between the special filter and the device for preliminary filtration a space which corresponds to the description set forth above. Each of these conditions may be effected by any suitable means, some of which are disclosed hereinafter by Way of example. The first condition may be realized, for example, by using very even tissues such as can be obtained by rolling, calendering or ironing or (in the case of synthetic filaments) by setting the tissue or tissues and subjecting them subsequently to a contracting treatment in order to stretchthem. The second condition may be met, for example, either by welding the periphery of the special filter to the front surface of the spinneret plate or by pressing said periphery toward said plate by means of a system of joints. A convenient means for realizing the third condition consists in interposing between the special filter and the device for preliminary filtration a circular member supporting a grid or perforated rigid plate, which is held in spaced position by means of studs or braces, and thereby supports the preliminary filtration unit.

It will be understood that there are very many possible embodiments of the units according to I the invention, and the example stated below should not be considered limitative in any re,- spect, i. e. neither with rega lizi p the selection nor with regard to the arrangement of the various parts forming the equipment according tothe invention. This example demonstrates particularly clearly the considerable technical progress obtainable in the spinning of high polymers by the use of the device according to the invention, since it is possible thereby. to reduce the frequency of chan i g the spinnerets'to an extent not known up to date; a

. x mp A2472; solutionoi cellulose ac eta.te in acetone is extruded in a; known manner-from a dry spinnin'g'cell in order to obtain a thread of 100 deniers-18 fila;ments. H a

A unit'su-itable for carrying out the invention is illustrated in the accompanying drawing, in which :1

Figfl is a central vertical section through the unit; a d

2 me r g-W t e .7, Int he drawing 'l designates a nut in threaded a meniw m ans terip l h ad member t imm the e d ort on of conduit 2 hi pp sii hespim ns a ti i, A spinneret plate 3 of unoxidizable steelof a thickness of 2' mm. is threaded intosaid nut and is provided with 18 extrusion apertures 4, each of which has a crosst en i l- 5mm? a hep fljet d m at the inlet. Directly on said plate is placed a dishithe diameterofwhich is; equal to that of the spinneret plateand which comprises two previously calendered bronzelgauzes in the surface of, which the inters ticesi between the threads have awidth:of 0,003 mml and; two layers of a superpolyamide- =fiber satin, in which the average width of V the interstices is 0.001 mmfi. The ,edges of'these four layers are glued on their entire circumference by means of a superpolyamide'varnish, Member 6 isa metal-plastic ring of '3 n i-1n. thickness, the compression of which ensuresthelateral tightness of the unit in such a manner that the solution cannot pass around member 5 and is compelled to traverse said member, A rigid plate 1 ofunoxidizablesteel of 3,mm-. 'thickness is provided with apertures in communication with the V separating space 8. Above theplate I there is a second disk 9 which is formed ofa bronze gauze and a layer of superpolyamide fiber satin similar to those in the member 5,. which are set by means of brass. Member .Hlis a preformed plate of plastic material, which simultaneously forms a joint and ensures tightness between the unit members i, it and ll,.the latterbeing as above stated the end portion of the conduit supplying the spinning solution. Above the preliminary filtration unit is a-filtering layer I2 of a known and customary According to a modified embodiment of this ,device, .-thefspinneret r plate. may be held in the tion, a threaded member having a large central opening may be interposed between the perforated plate l0 and the coupling of conduit 1 l and such member would provide for fixing and compression of the various member's'even before the unit is mounted on the supply tube of the spinning solution.

The number of spinnerets to be put in action in order to correctly start a spinning frame by meansof the units thus constructed is 6% lower than that necessary in the use of the usual spinnerets. The periodof spinning before it becomes necessary to change the spinnerets is 20 to times higher compared with a frame provided with a a usual type. of spinnerets.

It will be understood by those skilled in the art that the present invention is not limited to the specific details described or shown and may be carried out with various modifications. Thus, soldering may be us djinstead 6f welding and other varnishes inay'beiusd in's'tad'of the superpolyamide varnishforconnecting the filter layers at their circumrereiiee; ''iEurthrfn'dr'e, the thickness of ring 6 shown "in the "drawing may be less than 3 mm., althou gh it must have a thickness holding the device for *preiiminar filtration at a distance of at least 1 :min. from the. special filter. These and other;;modifications may be made without departing from the scope of the invention as defined in the appended claims.

We claim as our invention: I

1. A device for spinning a solutio'n 'ofhigh polymers, including a spinneret 'plate of rigid metal provided with extrusion orifices havin' gj'a cross-sectional area at the inlet equal to at least 50 times the. cross sectional area at theoutlet, comprising, in combination, a spinneret plate filter placed on said plate, said filter beingin contact with said plate over its entire surface and covering .all offsaid orifices, said spinneret plate filtercomprising atleast. one fabric formed of filaments of synthetic resinousim-aterial, said filaments having a substantially circular crosssection and cylindrical shape, said fabric containing at least 10,000 interstices per square centimeter between the'thread crossings, the average area of said interstices being smaller thanjthe cross-sectional area at the outlet end of saidex trusion orifices, and being equal, to at most;0.003 square millimeter, and, spaced from the spinneret plate filter and separated therefrom by a hollow space of at least 1 mm. thickness, a preliminary filter containing at least onerfabric formed of filaments of synthetic resinous material, in order to' permit the solution issuing, fromhall points of the preliminary filter,..to reach any. of the extrusion orifices, said filamentshaving asub: stantially circular cross-section andv cylindrical shape, said fabric containing at least 10,000 interstices persquare centimeter between the, thread crossingsfthei average area er 'saidjinterstices being smaller. than the cross-sectional area at the outlet end of said extrusion orifices and being equal to at most 0.003 .squaremillimeter.

2. A device .of vthe type claimedin claim '1,

in which the spinneret plate filter..cons'ists oi two 'calendered bronze gauzes, in which the average area of interstices amountsito about 0.003 mm. andtwo layers of superpolyamide'fibersatin, in which theaverage area of the interstices is '0.001 mm. the edges of these four layers being glued on their entire circumference n t s nn nas l i insj i h h P l 'mers, in which adevi ce as claimed in claiml,

is tightly enclosed in a tubular member havin a cylindrical inner surface and in which the spinneret plate filter consists of two calendered bronze gauzes, in which the average area of interstices amounts to about 0.003 mm. and two layers of superpolyamide fiber satin, in which the average area of the interstices is 0.001 mm.

" the edges of these four layers being glued on their contact with said plate over its entire surface and covering all of said orifices, said spinneret plate filter comprising at least one fabric formed of filaments of synthetic resinous material, said filaments having a substantially circular crosssection and cylindrical shape, said fabric containing at least 10,000 interstices per square centimeter between the thread crossings, the average area of said interstices being smaller than the cross-sectional area at the outlet end of said extrusion orifices and being equal to at most 0.003 square millimeter, and, spaced from the spinneret plate filter and separated therefrom by a hollow space of 1-3 mm. thickness, a preliminary filter containing at least one fabric formed of filaments of synthetic resinous material, in order to permit the solution issuing from all points of the preliminary filter, to reach any of the extrusion orifices, said filaments having a substantially circular cross-section and cylindrical shape, said fabric containing at least 10,000 interstices per square centimeter between the thread crossings, the average area of said interstices being smaller than the cross-sectional area at the outlet end of said extrusion orifices and being equal to at most 0.003 square millimeter.

5. A device for spinning solutions of high polymers, in which the solution is forced through a preliminary filter which contains at least one fabric formed of filaments of synthetic resinous material, said. filaments having a substantially circular cross-section and cylindrical shape, said fabric containing at least 10,000 interstices per square centimeter between the thread crossings, the average area of said interstices being equal to at most 0.003 square millimeter and then through a spinneret plate filter spaced from the preliminary filter and separated from ;:the latter by a hollow space and a perforated "plate supporting the preliminary filter substantially on its entire surface, said spinneret plate'filter containing at least one fabric formed of filaments of synthetic resinous material, said filaments having a substantially circular cross-section and cylindrical shape, said fabric containing at least 10,000 interstices per square centimeter between the thread crossings, the average area of said.

interstices being equal to at most 0.003 square millimeter.

- PIERRE SALE.

JOSEPH A. TRILLAT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Apr. 23, 19 23 

1. A DEIVCE FOR SPINNING A SOLUTION OF HIGH POLYMERS, INCLUDING A SPINNERET PLATE OF RIGID METAL PROVIDED WITH EXTRUSION ORIFICES HAVING A CROSS-SECTIONAL AREA AT THE INLET EQUAL TO AT LEAST 50 TIMES THE CROSS-SECTIONAL AREA AT THE OUTLET, COMPRISING, IN COMBINATION, A SPINNERET PLATE FILTER PLACED ON SAID PLATE, SAID FILTER BEING IN CONTACT WITH SAID PLATE OVER ITS ENTIRE SURFACE AND COVERING ALL OF SAID ORIFICES, SAID SPINNERT PLATE FILTER COMPRISING AT LEAST ONE FABRIC FORMED OF FILAMENTS OF SYNTHETIC RESINOUS MATERIAL, SAID FILAMENTS HAVING A SUBSTANTIALLY CIRCULAR CROSSSECTION AND CYLINDRICAL SHAPE, SAID FABRIC CONTAINING AT LEAST 10,000 INTERSTICES PER SQUARE CENTIMETER BETWEEN THE THREAD CROSSING, THE AVERAGE AREA OF SAID INTERSTICES BEING SMALLER THAN THE CROSS-SECTIONAL AREA AT THE OUTLET END OF SAID EXTRUSION ORIFICES AND BEING EQUAL TO AT MOST 0.003 SQUARE MILLIMETER, AND, SPACED FROM THE SPINNERET PLATE FILTER AND SEPARATED THEREFROM BY A HOLLOW SPACE OF AT LEAST 1 MM. THICKNESS, A PRELIMINARY FILTER CONTAINING AT LEAST ONE FABRIC FORMED OF FILAMENTS OF SYNTHETIC RESINOUS MATERIAL, IN ORDER TO PERMIT THE SOLUTION ISSUING FROM ALL POINTS OF THE PRELIMINARY FILTER, TO REACH ANY OF THE EXTRUSION ORIFICES, SAIF FILAMENTS HAVING A SUBSTANTIALLY CIRCULAR CROSS-SECTION AND CYLINDRICAL SHAPE, SAID FARBIC CONTAINING AT LEAST 10,000 INTERSTICES PER SQUARE CENTIMETER BETWEEN THE THREAD CROSSING, THE AVERAGE AREA OF SAID INTERSTICES BEING SMALLER THAN THE CROSS-SECTIONAL AREA AT THE OUTLET END OF SAID EXTRUSION ORIFICES AND BEING EQUAL TO AT MOST 0.00O SQUARE MILLIMETER. 